In the background is the end of the ice sheet where
blocks of ice fall off into the sea to melt and/or be carried
away. The foreground is an area of shallow water just
a few inches deep where in some areas there were steady streams
of bubbles rising to the surface, you can see four of them at
the bottom of this picture. The bubbles were small but raising
rapidly like those produced by an air pump in an aquarium. Quite
how any air came to be trapped and escaping in this way was
another puzzle that I couldn't answer.